Patent CA-1209376-A (CA)
Inventor: KERR JOHN H
IPC: F16H3/091
Filed: 1984-05-29
Granted: 1986-08-12
Abstract: a) Title Incrementally Variable Single Countershaft Transmission. b) Abstract of the Disclosure Incrementally  Variable  Transmissions  with  single  countershaft structures,  and  series structures that combine  two  or more single countershaft structures are disclosed herein.    A single countershaft  structure  consists  of  coaxially  mounted input and and output shafts,  with one gear  element in each pair of a sequence of gear-pairs fixed to the countershaft, with the second gear element of the first two pairs free to rotate on the input shaft,  and the remaining second gear elements free to rotate on the output shaft.          The ratios of  the 1st  and 2nd pair are  referenced from the input to the countershaft  with  the ratios of the remaining  pairs  referenced from the countershaft to the output shaft.   The ratios of any single countershaft structure are selected by  a mechanism,  consisting of a shift  gate with  profiled slots that move the shift  forks of  sliding dog  couplers between each gear-pair,  so that either the 1st,  or 2nd gear-pair is  coupled to the input shaft, in combinations with  the remaining gear-pairs that are coupled to the output shaft, begining with the last pair of the sequence.   The order of mutual dependency  in the combinations of gear-pairs, requires that  the ratios  in  the sequence  be substantially X*y,  y, X2/y,  .   .   X2(N-1)-2/y,  X2N-2/y, where:  N is the total number of gear-pairs,  y is the ratio  of the 2nd gear-pair,  and X is the basic increment of change in  the effective ratios of the combinations,  and is  the inverse root of the number of ratios less one,  of the maximum ratio of the structure.    The disclosed  single countershaft  transmissions  may  be  either output speed decreasing or increasing,  with  the decrements of change in the continuum ratios respectively  from either a minimum  when X is less than one, or a maximum when X is greater than one, to unity.   The total number of continuum ratios in the transmissions with the disclosed series arrangements is the product of the number of ratios in each of the single countershaft structures,  with the ratios in the sequence  of gear-pairs  of any added structure of the same order  of those of any single countershaft structure, but with the value of X in the sequence substantially equal to X multiplied by the maximum  ratio of  the series up to the addition of  the next  structure  in  the ar-rangement.   The mutual dependency in the combinations of each struct-ure is  maintained,  with  the ratios  of each  structure permuted in combinations with  those of  the other structures to provide  the con-tinuum ratios in the transmission. c) Background of the invention (i)  Field of the invention The present invention relates to manual countershaft transmissions that are  used in  road and  off-road vehicles,  machinery,  and other drive applications,  where there is  a need to alter either the torque or the speed of the output from the prime mover.          (ii)  Description of the Prior Art The structures of present manual  countershaft  transmissions  in-corporate one gear-pair for each selectable ratio, with the gear-pairs selected independently either in or out of continuum.   This method of selecting  the ratio  changes in countershaft transmissions requires a large number of gearpairs  and relatively complex  selecter mechanisms when more than five ratios are required.   The following patents reflect the state-of-the-art techniques used to select the ratios in present manual countershaft transmissions:          US 329,332 "Four Speed Change Speed Gear" Molly-January 10,33 Can 720,214 "Gear Changing Mechanism" Gronau-October 26, 1965